An arrangement for detecting a changing operating parameter of the kind referred to above can be utilized especially for angle measurement in an internal combustion engine and is disclosed in European patent publication no. 0,118,247. The two measuring devices generate respective signal values which represent the operating parameter to be detected. A linear characteristic is pregiven for one of the measuring devices and is dependent on the parameter to be detected; whereas, another measuring device has this linear characteristic only in selected signal value ranges and does not generate signal values outside of this range. These signal value ranges are pregiven with reference to a function monitoring of the measuring devices and/or of the system by means of plausibility comparisons of the signal values of the measuring devices.
Since the measuring devices have a common voltage supply, irregularities and especially value fluctuations in the supply voltage lead to incorrect measuring results and therefore to malfunctions of the internal combustion engine and/or of the system connected to the measuring devices which cannot be detected by the plausibility monitoring referred to above.